I. Field of the Invention
This invention relates generally to an electrical cardiac pacing and/or sensing lead and a method of treating heart failure using such lead to optimize hemodynamic performance of a sick heart. More particularly, this invention relates to an elongated, thin, flexible lead having a laser banded electrode surface adapted for placement in a selected coronary vein. The lead may include a transition ring that further assists the user in guiding the lead through a coronary vein. Also, a method is provided for delivering a lead to a predetermined region of a patient's heart and then stimulating the left ventricle, without a need for implanting a pacing lead within the left ventricular chamber.
II. Discussion of the Related Art
In the past, transveneously inserted leads for implantable cardiac pacemakers have principally been positioned within the right atrium or right ventricle of the patient's heart for pacing the right atrium and/or right ventricle, respectively. While it is relatively safe to insert a pacing lead and associated electrode(s) into the right atrium or right ventricle, there is a reluctance to install a similar lead into the left ventricle because of the possibility of clot formation and resulting stroke.
When a lead is implanted within a patient's circulatory system, there is always the possibility of a thrombus being generated and released. If the lead is positioned in the right atrium or right ventricle, a generated thrombus tends to migrate through the pulmonary artery and is filtered by the patient's lungs. A thrombus generated in the left atrium or left ventricle, however, would pose a danger to the patient due to the possibility of a resulting ischemic episode.
Thus, in those instances where left heart stimulation is desired, it has been a common practice to use an intercostal approach using a myocardial screw-in, positive-fixation lead. The screw-in lead may, however, be traumatic for the patient. There are additional instances when left ventricular pacing is desired, such as during bi-ventricular pacing. Mower, in U.S. Pat. No. 4,928,688 (hereinafter "the '688 patent"), describes an arrangement for achieving bi-ventricular pacing in which electrical stimulating pulses are applied, via electrodes on a single pacing lead, to both the right and left ventricular chambers so as to obtain a coordinated contraction and pumping action of the heart. The '688 patent discloses a split pacing lead having first and second separate electrodes, wherein the first electrode is preferably introduced through the superior vena cava for pacing the right ventricle and the second electrode is introduced through the coronary sinus for pacing the left ventricle. The lead and method described in the '688 patent is limited in placement of the second electrode within the coronary sinus. Hence, there is a need for a lead having a construction suitable for placement in the coronary veins including the posterior veins, the middle veins or the great vein.
Other electrode leads which are inserted into the coronary sinus have been described. For example, in U.S. Pat. No. 5,014,696 to Mehra and U.S. Pat. No. 4,932,407 to Williams there is disclosed an endocardial defibrillation electrode system. They each disclose transveneously inserting an electrode lead into the coronary sinus and great vein of a patient's heart, but in each case the lead does not extend through the great vein downward towards the apex of the heart. The leads disclosed by Mehra and Williams are limited to use in conjunction with either another lead inserted in the right ventricle or a large subcutaneous surface patch electrode in order to apply a defibrillating shock to a patient's heart.
A lead and method suitable for pacing the left ventricle of a patient's heart in accordance with the present invention is not disclosed in the related art. The related art does not disclose a lead that may be used to improve the synchronization and/or coordination of the contraction of the chambers of the heart or pace all four chambers of the heart with two leads, wherein the lead has a laser banded electrode surface adapted for placement in a selected coronary vein. Also, the current leads may not be easily rotated and guided into the coronary vein of a patient. Hence, a need exists for a lead and method of pacing a patient's heart to achieve a desired synchronization, wherein the lead has a diameter, flexible tip and physical properties and rotational ability suitable for positioning it in any of several coronary veins, to thereby selectively pace the left ventricle, left atrium, right atrium or a combination thereof The present invention meets these needs and overcomes other disadvantages of the prior art.